For decades, scientists have worked toward the dream of harnessing a fusion reaction. Fusion, which involves the joining together of two light atomic nuclei, should produce much more energy and much less radioactive waste than the current nuclear reactors which are based on fission (splitting) of uranium. Unfortunately, making a controlled fusion reaction has proved a lot harder than many people would have thought. For years, the joke has circulated through energy circles: fusion is the power source of the future, and it always will be. Things are not completely bleak on the fusion front. Just last week, France was selected as the site for a massive international effort to build the first practical fusion reactor. If all goes as plans, the reactor could be operational by the end of the decade. Maybe.

But this diary isn't about fusion. It's about that other kind of nuclear reaction, the kind in use around the world today -- fission. It's about how we might be able to make fission not only cleaner, but 100% safe.

The essence of a conventional nuclear reactor is the controlled fission chain reaction of U-235 and Pu-239. This produces heat which is used to make steam which drives a turbine. The chain reaction depends on having a surplus of neutrons to keep it going (a U-235 fission requires one neutron input and produces on average 2.43 neutrons).

That's the way it's been since the first commercial reactors were started up in the 1950's. Put in uranium, extract an admix of uranium, plutonium, and assorted byproducts.

Only the reasons for using uranium don't all have to do with producing power. In fact, reactors were designed around uranium for a very different reason.

... design challenges and a Cold War-era interest in using nuclear waste byproducts in atomic bombs pushed the industry to use uranium as its primary fuel.

Uranium was picked, not because it was the cleanest or safest possible fuel, but because it was both dirty and dangerous. Its waste products include everything you need to start up your own Cold War era bomb assembly line - which is exactly why we're so antsy about Iraq having nuclear reactors based on this fuel. Building uranium reactors was easy, since the reaction is self-sustaining, which is exactly why it's also easy to have a reaction run out of control.

Traditional power plants, which involve fuel rods stuffed with pellets of uranium regulated by various means, had some degree of inherent instability. Some of these designs are worse than others (i.e. Chernobyl). Newer power plant designs, like the Pebble Bed Reactor enclose the uranium fuel in small "pebbles" that make it nearly impossible for the reactor to ever run out of control.

But what if there was another choice? What if you didn't run your fission reactors on uranium at all? What if you ran them on another element, one that's much more common, produces less overall waste, and whose use creates much less of the plutonium suitable for making nuclear weapons? What if you ran reactors on thorium?

Why throrium? First of all, it's a lot more abundant than uranium.

For many years there has been interest in utilizing thorium (Th-232) as a nuclear fuel since it is three times as abundant in the earth's crust as uranium. Also, all of the mined thorium is potentially useable in a reactor, compared with the 0.7% of natural uranium, so some 40 times the amount of energy per unit mass might be available.

40x as much energy available from thorium, and thorium is not only available in the United States (which has a decent supply of uranium), but also in countries where uranium is much more scarce. Further, since thorium can't be as easily refined to make nuclear weapons, it can be shipped around the world with less concern.

If we were running our reactors on thorium, we would produce much less waste. If Iraq was running its reactors on thorium, we'd be a lot less concerned about them turning spent fuel into weapons. So why don't we run on thorium?

Well, there's a problem.

A thorium reactor would work by having Th-232 capture a neutron to become Th-233 which decays to uranium-233, which fissions. The problem is that insufficient neutrons are generated to keep the reaction going.

Oh. That sounds pretty bad, huh? A reaction that can't be sustained is back into fusion land - looks good, but not very practical. However, what looks like a problem on the surface, is actually another benefit of using thorium as a fuel. It is possible to sustain a reaction in a thorium-based reactor, but to do so you have to stimulate it using an "Accelerator Driven System," or ADS. In an ADS, a high energy accelerator is used to spawn additional neutrons through a process called "spallation". This does make sustaining the reaction more complicated, but it has a big advantage: turn off the ADS, and the reaction stops. A "subcritical," ADS-based reactor can never run out of control.

So thorium is more abundant than uranium, a reactor based on thorium makes it much tougher to make weapons, and a thorium reactor can never "go Chernobyl." How about nuclear waste?

Fueling nuclear reactors with the element thorium instead of uranium could produce half as much radioactive waste and reduce the availability of weapons-grade plutonium by as much as 80 percent.

There's one other big advantage of using an ADS system. With it, you can "burn" some of the waste products (in this case, the actinides) down to stable isotopes, eliminating a good percentage of the waste. It's not an absolute positive, as the short-term result is even more energetic radioactive isotopes, but over a longer period, the resulting waste should be less radioactive than uranium ore.

With all these advantages, thorium has finally started to get some attention over the last few years. There's been some significant research in both the United States and Russia, and for nearly a decade, India has been running a research reactor on uranium-233 created from thorium fuel. Now India is getting ready to make the next step. They're going to test their own ADS-based, thorium reactor. They have high hopes, and so does the thorium mining industry.

And in January, India -- which has the world's second largest reserve of thorium behind Australia --announced it would begin testing the safety of a design of its own.

The anticipated surge in demand for thorium has led at least one mining company to begin buying as many thorium deposits and stockpiles as it can.

"We feel that it's inevitable that the U.S. and other countries in the world -- India of course -- will exclusively use thorium in the future," said Novastar Director of Strategic Planning Seth Shaw.

How likely is Shaw's "we all move to thorium" scenario? Unfortunately, none too likely -- at least, not in the short term. The current nuclear industry is entrenched in the uranium business. From mining to refining to the reactor, uranium is what they know. Market prices currently put the cost of thorium only slightly below uranium, not enough to cause any major company to consider making the switch.

However, there's one factor overlooked in the current pricing - the cost of waste disposal.

As an interim solution, the United States could change the way it charges power plants for the nuclear waste that they produce, said Kazimi.

Currently, waste fees are calculated as a fraction of the cost of the electricity that is produced by the fuel. Kazimi proposes charging by the volume of plutonium instead, so as to discourage its creation.

Current waste fees are calculated only on the output of the plant, with no regard to the toxicity of the waste. If waste fees were calculated so that the creation of plutonium was discouraged, thorium would suddenly look a lot more attractive to the US industry.

Changing this fee structure is just one of the many items that should be involved in a effective national energy policy. It's one of those minor things, easy to overlook in the glut of new tax breaks for oil companies, that might just lead us to safer power plants.

Occasionally power reactors in the US have released radionuclides in insignificant amounts. The NRC strictly regulates the permissible amount and the average annual radiation from nuclear plants falls way below that. From coal plants, about a hundred times more radioactivity is released. It's unregulated. So is coal waste. An average plant concentrates enough U-235 a year to make several atomic bombs.

People assume that the steam coming out of cooling towers of nuclear plants must be radioactive. In fact it's from a secondary or tertiary, closed system--it's entirely separate from the water cooling the reactor core.

No question that nuclear power is cleaner and safer than fossil fuel power, as a study by the EU stated several years ago.

No question that if uranium supplies run low thorium could be used instead.

Incidentally, people living in the part of India where there are thorium formations are exposed to very high levels of natural background radiation--higher than those exposures found around Chernobyl. Several hundred millirem And the population is doing fine, as is a population in China living on thorium sands.

You're welcome. The truth is just not sensational enough to satisfy media appetities.

Unfortunately, sensational coverage about nuclear power scares people and this is very helpful to the coal industry, which is growing rapidly. Germany, for example, is increasing its reliance on coal combustion. About a hundred new coal plants are likely to be built in the US.

I wish 60 Minutes would do a show about the large number of deaths caused by fossil fuel combustion. Those figures are well-documented.

People around nuclear plants get more exposure to radioactivity from eating bananas and legumes. They contain a radioactive isotope of potassium. In fact, we all get an average of 39 millirem per year from the food we consume.

I am not afraid of nuclear power, having investigated its risks. You know what I am afraid of? Global warming. Its effects will cause millions of deaths of humans and extinction of many species.

We have the solution right now to mitigating human contribution to global warming while providing baseload electricity.

I am prepared to believe that nuclear power generation is safer in operation and in emissions than hydrocarbon-fuelled power, but what about the radioactive waste? But can we guarantee safe storage for the necessary (very lengthy!) period of time?

Nope, you can't guarantee ANYTHING. What you can do is get the waste problem to the point where the probability of a resultant death is comparable to (or, as currently required, orders of magnitude less than) the probability of a death from, say, coal mining, for the same amount of energy.

For various historical reasons nuclear power is held to impossibly high standards of perfection, while we accept high fatality rates in coal and hydroelectric power generation.http://www.uic.com.au/ne6.htm

I am curious about this anecdotal evidence of the "safety" of radiation exposure as it directly contradicts the most recent NAS report

WASHINGTON - June 30 - The National Academies of Science released an over 700-page report yesterday on the risks from ionizing radiation. The BEIR VII or seventh Biological Effects of Ionizing Radiation report on "Health Risks from Exposure to Low Levels of Ionizing Radiation" reconfirmed the previous knowledge that there is no safe level of exposure to radiation--that even very low doses can cause cancer. Risks from low dose radiation are equal or greater than previously thought. The committee reviewed some additional ways that radiation causes damage to cells.

Radiation causes other health effects such as heart disease and stroke, and further study is needed to predict the doses that result in these non-cancer health effects.

It is possible that children born to parents that have been exposed to radiation could be affected by those exposures.

The "bystander effect" is an additional, newly recognized method by which radiation injures cells that were not directly hit but are in the vicinity of those that were. "Genomic instability" can be caused by exposure to low doses of radiation and according to the report "might contribute significantly to radiation cancer risk." These new mechanisms for radiation damage were not included in the risk estimates reported by the BEIR VII report, but were recommended for further study.

The Linear-No-Threshold model (LNT) for predicting health effects from radiation (dose-response) is retained, meaning that every exposure causes some risk and that risks are generally proportional to dose. The Dose and Dose-Rate Effectiveness Factor or DDREF which had been suggested in the 1990 BEIR V report to be applied at low doses, has been reduced from 2 to 1.5. That means the projected number of health effects at low doses are greater than previously thought.

RADIATION RISKIER THAN THOUGHT-- RISKS TO PUBLIC and NUCLEAR WORKERS

The BEIR VII risk numbers indicate that about 1 in 100 members of the public would get cancer if exposed to 100 millirads (1milliGray) per year for a 70-year lifetime.[1] This is essentially the US Nuclear Regulatory Commission's allowable radiation dose for members of the public.

In addition, 1 in about 5 workers[2] would get cancer if exposed to the legally allowable occupational doses[3] over their 50 years in the workforce. These risks are much higher than permitted for other carcinogens.

Specifically, the US Nuclear Regulatory Commission allows members of the public to get 100 millirems or mr (1 milliSievert or mSv) per year of radiation in addition to background. The BEIR VII report (page 500, Table 12-9) estimates that this level will result in approximately 1 (1.142) cancer in every 100 people exposed at 100 mr/yr which includes 1 fatal cancer in every 175 people so exposed (5.7 in 1000)[4].

The risk of getting cancer from radiation (in BEIR VII) is increased by about a third from current government risk figures (FGR13):

BEIR VII estimates that 11.42 people will get cancer if 10,000 are each exposed to a rem (1,000 millirems or 10 mSv).

The US Environmental Protection Agency Federal Guidance Report 13 estimates that 8.46 people will get cancer if 10,000 are each exposed to a rem. [... more ...]

In other words the US scientific establishment, despite various pressures from the nuke and energy lobby, has officially declared that its previous take on the danger of low-dosage radiation risk was overly optimistic and has revised its risk estimates upward, not downward.

In light of this one has to suspect that indigenous populations living on or near natural geologic radiation sources (a) are reproducing fast enough to compensate for attrition from cancer and related effects and thus appear to be "doing fine" despite a steady component of radiation-related mortality, or (b) over centuries have been selected genetically for resistance to radiation damage. Presumably populations without this adaptation would not fare so well...

I recall reading that the current fission reactors
are all based on the design originally used for nuclear submarines. They were not necessarily the best design, but were used simply because there was the experience of
using that type of reactor.